Positive displacement pump

ABSTRACT

A positive displacement double-acting piston pump wherein a shaft drives a disc to which is pivotally secured a piston. The piston is connected to the pump casing, and on rotation of the disc oscillations of variable eccentricity are carried out by the piston. The disc has seals whereby the piston divides the casing into two mutually sealed chambers of variable volume.

I United States Patent 1 [111 3,765,805 Juhasz Oct. 16 1973 POSITIVE DISPLACEMENT PUMP 3,552,895 l/l97l Bayley 418/178 5] Inventor: ajos J Han/an ga y 2,215,873 9/1940 Gahm 418/60 X [73] Assignee: Konzerv-Es Paprikaipari FOREIGN PATENTS OR APPLICATIONS Kutatointezet, Budapest, Hungary 789,375 1/1958 Great Britain 417/481 [22] Filed: July 7, 1971 Primary Examiner-Carlton R. Croyle [21] Appl' 160437 Assistant Examiner-Richard E. Gluck AtzorneyYoung & Thompson [30] Foreign Application Priority Data July 23, 1970 Hungary KO-2355 [57] ABSTRACT [52] U.S. Cl 418/68, 417/481, 11186117681, A positive displacement double acting piston Pump [51] Int Cl Folc l/oo F04c 21/00 wherein a shaft drives a disc to which is pivotally se- [58] Fieid 418/68 176 161 cured a piston. The piston is connected to the pump 418/186 casing, and on rotation of the disc oscillations of variable eccentricity are carried out by the piston. The disc has seals whereby the piston divides the casing [56] g ggg gi into two mutually sealed chambers of variable volume.

2,151,848 3/1939 Griinen 417/484 9 Claims, 6 Drawing Figures POSITIVE DISPLACEMENT PUMP This invention relates to a positive displacement pump of simple construction and reliable operation in which, in operation, volume displacement proceeds without a valve and liquid transfer takes place with the aid of a disc rotating in an enclosed space and having a rotary piston attached to it.

The most widely used type of pump is the valved piston pump, of which numerous constructions are known. Its disadvantages include the high cost of manufacture, the considerable work involved in carrying out repairs because of the valve and of the associated crank mechanism which is necessary to convert the rotary movement of the prime mover into a rectilinear reciprocating movement of the piston, and the considerable space requirements.

In addition, a variety of rotary positive displacement pumps not using a valve are known. Pumps with a single, concentrically fitted rotor and a sliding-valve seal have the disadvantage of liability to wear and the abrasive effect of the valve, the necessity for springs to be incorporated, and, further, that the liquid path is blocked along a single line. Pumps with rotating valves and rotating blades display the appreciable defect of being liable to wear at their casing and blades because of the centrifugal forces acting on the latter.

In the known pumps using duplex rotor displacement elements, too, the suction and pressure sides are mutually separated by one or more sealing edges. To the disadvantages of high manufacturing costs displayed by these pumps must be added the relatively rapid wear of the sealing edges, the consequent rapid fall in the volumetric efficiency of the pump, substantial mechanical losses, the susceptibility to damage and the complicated nature and expense of carrying out repairs.

An alternative known positive displacement pump is the gear pump with two rotors. However, both the external and internal types of gear pump display the disadvantage of requiring a complicated manufacturing process. In these pumps the suction and pressure spaces are mutually delimited by the tooth profile of the liquid-conveying gears along a single contact edge (line). Relatively rapid wear is thus inevitable even if a separate pair of driving gears is incorporated in addition to the pair of gears serving for the liquid transfer, because wear of the driving gears leads to wear of the transfer gears. The result is a tapering down of the teeth after only a relatively short use. The losses in the gap thus formed lead to a diminished pumping rate. This gap formation (lack of tightness) impairs the efficiency of pumping especially when liquid is conveyed between chambers at different pressures. The necessarily constant axial spacing requires expensive repairs result from operational wear. The necessary shaft seals are expensive, complicated and unreliable in the long term. Changing a single bearing or packing necessitates the complete dismantling of the pump and thus involves considerable effort.

Screw pumps with two or more rotors are further examples of positive displacement pumps, and are highly efficient. However, their manufacture is expensive, the pump components require to be accurately machined, they are sensitive to contamination and dry running, even briefly, leads to rapid destruction of the internal sealing surfaces.

All hitherto known positive displacement pumps share the defects of relatively high manufacturing cost, sensitivity to demage or other adverse factors and complicated, time-consuming and expensive repair work.

An aim of this invention is to eliminate or reduce the disadvantages of known positive displacement pumps.

According to the present invention, there is provided a positive displacement pump comprising a pump casing, a cover for the casing, a fluid inlet and a fluid outlet in the pump casing, a rotary drive shaft, an entraining member drivingly connected to the drive shaft, a piston pivotally connected for movement with the entraining member and formed with a recess, eccentric means secured to said cover and slidably engaging in said recess for reversibly oscillating the piston with variable eccentricity, and sealing means on the entraining member disposed so that the piston divides the interior of the pump casing into two mutually sealed chambers of variable volume, whereby on rotating the shaft through 360 the said chambers are each connected twice to said inlet and to said outlet to produce a double-acting pump.

Preferably the entraining member is a disc sealingly connected to said shaft, the sealing means being constituted by two peripheral arcuate, segmental lands on the disc. 7

The eccentric means may consist of a radially displaceable stay bolt detachably secured to the cover, and a bearing surrounding the stay bolt and engaged in the recess.

In an advantageous embodiment, a wear resistant lining is provided on the wall of the recess engaging with the bearing.

Preferably a wear-resistant bush surrounds the bearing and is adapted to slide on one side of the recess only.

The disc may carry an upstanding, eccentrically disposed, integral pivot pin, and the piston has a bore in which said pin'is received.

The piston is preferably substantially tuning-fork shaped, with the limbs of the fork connected at their end remote from the stem of the fork, the bore being in the stem.

The invention will now be described, by way of example only with reference to the accompanying drawings,

in which:

FIG. 1 shows a pump according to this invention partly in front elevation and partly in section, and with its cover removed for the sake of clarity,

FIG. 2 is a section through the pump taken on line A-B of FIG. 1,

FIG. 3 is an enlarged perspective representation of the pump disc forming part of the pump of FIG. 1, and

FIGS. 4 to 6 are schematic views showing the pump disc and rotating piston of FIG. 1 during seccessive stages of operation.

Referring to the drawings, there is shown a rotary pump according to the invention. More particularly, referring to FIGS. 1 and 2a rotary disc 2 is arranged in a pump casing 1 and is readily detachably keyed to a pump shaft 3. The periphery of the disc 2 is constructed in such a way that the disc 2 serves for both opening and closing of the inlet and outlet openings (indicated by appropriate arrows) during rotation. A pin 4, rotatably supporting a rotary tuning-fork shaped piston 5 in a piston bore, is rigidly connected with the disc 2. A cover plate 6 serves to seal the pump casing I and is detachably secured thereto by any suitable means such as screwing, e.g., with headless screws and wing nuts.

A stay bolt 7 is detachably and eccentrically secured to the cover 6 and, according to the desired pumping rate, can be moved radially away from the centre of the cover 6 into a different bore constructed in and located along the vertical centre line of the cover 6.

The stay bolt7 is journalled in a cylindrical rolling bearing 8 inserted to make a lit in a wear-resistant bush which slides through respectively 180 alternatingly on either side ofa recess 9 formed in the piston and lined with wear-resistant shoes 10. During sliding, the outer periphery of the bush of the rolling bearing 8 accommodating the stay bolt 7 is in contact with only one surface of the track, i.e., makes contact withone of the shoes only on one side of the recess 9.

A liquid seal, indicated by cross-latching, between the shaft 3 and the casing 1 is provided by means of a packing sleeve. Via appropriate bearings the pump shaft 3 is connected to a reduction gear driven by an electric motor (not shown).

The perspective view of the pump disc .2 shown in FIG. 3 reveals that the disc 2 is provided with a central bore and is reinforced or thickened on both sides. These reinforcements a and b are in the form of peripheral, segmental lands constituting sealing means. The pin 4 is permanently secured to the disc 2 in the centre of the sealing element a. In order to ensure that there is sufficient space between the pin 4 and the centre of the disc 2, the sealing element a is thinner than the sealing element 17.

The top and bottom surfaces (as viewed in FIG. 1) of the piston S are provided with packings ll, 12 and are matched to the internal surfaces of the sealing elements a, b; while its left and right end surfaces (as viewed in FIG. 2) are so matched to the cover 6 and the disc 2, respectively, that the piston divides the interior of the casing 1 into two mutually sealed chambers of variable volume between which no flow of liquid can occur. The wear at the two ends of the piston 5 and of the inner surfaces of the sealing elements a and b can be compensated for by inserting sealing platelets of a thickness matching the degree of wear underneath the packings ll, 12.

The mode of functioning of the pump according to this preferred embodiment of the invention is as follows:

The shaft 3 is set in rotation by the electric motor and reducing gear. During rotation, the disc 2 serves as the entraining member for the rotating piston 5, seated on the pin 4 permanently secured to the rotating disc 2. The piston 5 is also supported on the stay bolt 7 via the rolling bearing 8 and by the bush surrounding the bearing 8 sliding longitudinally on one side or the other of the recess 9 altematingly after respective 180 turns of the shaft 3, i.e., on the shoes 10 located there.

On rotation of the disc 2 the piston 5 is deflected by a variable amount dependent on the distance between the pump shaft'3 and the stay bolt 7. The movement of the piston 5 produces suction, i.e'., an increase in volume, on one side. During this phase of the movement, the suction and delivery openings are in the open position. When the direction of oscillation of the piston 5 is reversed no communication obtains between the suction and delivery sides (suction and pressure cham bers), because the gaps between the disc 2 and the sealing elements a and b are closed. During rotation of the shaft 3 the pivot pin 4 approaches close to the stray bolt 7 and during the second half of the rotation moves away from same.

To ensure a balance between the loads operative within the pump the distance between the pin secured to the rotating disc and the stay bolt secured to the lid must be controlled in such a manner that the closest distance that the pin and bolt approach to one another is not less than the distance between the stay bolt and the upper edge of the piston, i.e., these distances should be approximately the same if possible.

FIG. 4 shows the disc 2 containing the piston 5 during the rotation phase when the sealing element a closes the suction (inlet) opening and sealing element b closes the delivery (outlet) opening. The chamber that has the larger volume during suction (shown shaded) is filled with liquid.

In the position shown in FIG. 5 both the suction and delivery openings are open and the pump sucks the liquid through the suction opening into the suctionside chamber which is increasing in volume, while liquid is forced out of the delivery chamber, which is of decreasing volume, through the delivery opening.

FIG. 6 shows a position similar to that illustrated in FIG. 4 i.e., both the suction and delivery openings are closed and the disc 2 moves the delivery chamber (shown shaded) filled with liquid in the direction of the delivery opening and the emptied chamber of reduced volume in the direction of the suction opening.

Because of its simple construction the pump according to the illustrated embodiment of the invention can be manufactured relatively cheaply, its operation is reliable and economic, its is notparticularly susceptible to interfering effects and faults are relatively easily diagnosed and eliminated. Assembling and dismantling, elimination of leaks and renewing of worn packings after prolonged use can be carried out very quickly. After removing the det'achably secured cover 6 from the casing l, the piston 5 can be simply pulled off the pivot pin 4. The gaps formed after prolonged use can be eliminated by laying platelets of a thickness matching the degree of wear underneath the insert incorporated at the two ends of the piston. The drive shaft, is simply and reliably sealed.

I claim:

1. A positive displacement pump comprising a pump casing having a fluid inlet and a fluid outlet, a rotary drive shaft extending through the casing, an entraining member carried by the drive shaft for rotation with the drive shaft in said casing, a piston carried by said entraining member for rotation with said entraining member in said casing, said piston dividing the interior of said casing into a pair of chambers of variable volume, means pivotally interconnecting said piston and said entraining member for pivotal movement of said piston relative to said entraining member about an axis eccentric to the drive shaft, said piston having a recess therein, and eccentric means secured to said casing and slidably disposed in said recess for reversibly oscillating the piston upon rotation of said entraining member.

2. A pump as claimed in claim 1, said casing having a cover in which said eccentric means are secured.

3. A pump as claimed in claim 1, and sealing means carried by said entraining member and cooperating with said piston to seal said chambers from each other.

4. A pump as claimed in claim 3, said entraining member being a disc, said sealing means comprising 8. A pump as claimed in claim 7, the piston having substantially the shape of a tuning fork having a stem and limbs branching from said stem and disposed on either side of said eccentric means, said limbs being connected at their ends remote from said stem, said bore being in said stem.

9. A pump as claimed in claim 1, the eccentricity of said eccentric axis being greater than the eccentricity of said eccentric means. 

1. A positive displacement pump comprising a pump casing having a fluid inlet and a fluid outlet, a rotary drive shaft extending through the casing, an entraining member carried by the drive shaft for rotation with the drive shaft in said casing, a piston carried by said entraining member for rotation with said entraining member in said casing, said piston dividing the interior of said casing into a pair of chambers of variable volume, means pivotally interconnecting said piston and said entraining member for pivotal movement of said piston relative to said entraining member about an axis eccentric to the drive shaft, said piston having a recess therein, and eccentric means secured to said casing and slidably disposed in said recess for reversibly oscillating the piston upon rotation of said entraining member.
 2. A pump as claimed in claim 1, said casing having a cover in which said eccentric means are secured.
 3. A pump as claimed in claim 1, and sealing means carried by said entraining member and cooperating with said piston to seal said chambers from each other.
 4. A pump as claimed in claim 3, said entraining member being a disc, said sealing means comprising two peripheral, arcuate, segmental lands on said disc.
 5. A pump as claimed in claim 1, and a wear-resistant lining on a wall of said recess engaging said eccentric means.
 6. A pump as claimed in claim 5, and a wear-resistant bush on said eccentric means that slides on one side only of said recess.
 7. A pump as claimed in claim 1, said pivotal interconnecting means comprising a pivot pin secured to said entraining member and a bore in said piston in which said pivot pin is rotatably disposed.
 8. A pump as claimed in claim 7, the piston having substantially the shape of a tuning fork having a stem and limbs branching from said stem and disposed on either side of said eccentric means, said limbs being connected at their ends remote from said stem, said bore being in said stem.
 9. A pump as claimed in claim 1, the eccentricity of said eccentric axis being greater than the eccentricity of said eccentric means. 